diff --git a/scrapy/newitem/builder/__init__.py b/scrapy/newitem/builder/__init__.py
new file mode 100644
index 000000000..85ef494bb
--- /dev/null
+++ b/scrapy/newitem/builder/__init__.py
@@ -0,0 +1,130 @@
+from collections import defaultdict
+
+from scrapy.utils.misc import arg_to_iter
+from scrapy.utils.python import get_func_args
+
+
+class BuilderField(object):
+
+    def __init__(self, *args, **kwargs):
+        self.expander = self.tree_expander(*args)
+        self.reducer = kwargs.get('reducer')
+
+    def tree_expander(self, *funcs, **default_expander_args):
+        """A pipe expander implementing tree logic
+
+        It takes multiples unnamed arguments used as functions of the pipe, and
+        keywords used as expander_args to be passed to functions that supports it
+
+        If an expander function returns a list of values, each value is used as
+        input for next expander function
+
+        Always returns a list of values
+        """
+
+        _funcs = []
+        for func in funcs:
+            accepts_args = 'expander_args' in get_func_args(func)
+            _funcs.append((func, accepts_args))
+
+        def _expander(value, expander_args=None):
+            values = arg_to_iter(value)
+            aargs = default_expander_args
+            if expander_args:
+                aargs = aargs.copy()
+                aargs.update(expander_args)
+            pipe_kwargs = {'expander_args': aargs}
+            for func, accepts_args in _funcs:
+                next = []
+                kwargs = pipe_kwargs if accepts_args else {}
+                for val in values:
+                    val = func(val, **kwargs)
+                    if hasattr(val, '__iter__'):
+                        next.extend(val)
+                    elif val is not None:
+                        next.append(val)
+                values = next
+            return list(values)
+
+        return _expander
+
+
+class ItemBuilderMeta(type):
+    def __new__(mcs, class_name, bases, attrs):
+        cls = type.__new__(mcs, class_name, bases, attrs)
+        cls._builder_fields = cls._builder_fields.copy()
+    
+        if cls.item_class:
+            for name, field in cls.item_class.fields.iteritems():
+                bfield = None
+                if name in attrs:
+                    bfield = attrs[name] 
+                else:
+                    if name not in cls._builder_fields and cls.default_builder:
+                        bfield = cls.default_builder
+                        #actually add the field to the class
+                        setattr(cls, name, bfield)
+                if bfield:
+                    cls._builder_fields.add(name)
+        return cls
+
+
+class ItemBuilder(object):
+    __metaclass__ = ItemBuilderMeta
+
+    item_class = None
+    default_builder = None
+
+    _builder_fields = set()
+
+    def __init__(self, response=None, item=None, **expander_args):
+        self._response = response
+        self._item = item if item else self.item_class()
+
+        self._expander_args = {'response': self._response}
+        if expander_args:
+            self._expander_args.update(expander_args)
+
+        self._values = defaultdict(list)
+
+    def add_value(self, field_name, value, **new_expander_args):
+        field = self._get_builder_field(field_name)
+        evalue = self._expand_value(field, value, **new_expander_args)
+        self._values[field_name].extend(evalue)
+
+    def get_item(self):
+        item = self._item
+        for field in self._values:
+            item[field] = self.get_value(field)
+        return item
+
+    def get_value(self, field_name):
+        field = self._get_builder_field(field_name)
+        reducer = field.reducer or self._item.fields[field_name].from_unicode_list 
+        return reducer(self._values[field_name])
+
+    def replace_value(self, field_name, value, **new_expander_args):
+        field = self._get_builder_field(field_name)
+        evalue = self._expand_value(field, value, **new_expander_args)
+        self._values[field_name] = evalue
+
+    def _get_builder_field(self, name):
+        if name not in self._builder_fields:
+            raise KeyError
+
+        return getattr(self, name)
+
+    def _expand_value(self, field, value, **new_expander_args):
+        if new_expander_args:
+            expander_args = self._expander_args.copy()
+            expander_args.update(new_expander_args)
+        else:
+            expander_args = self._expander_args
+
+        evalue = field.expander(value, expander_args=expander_args)
+
+        if not isinstance(evalue, list):
+            evalue = [evalue]
+
+        return evalue
+
diff --git a/scrapy/newitem/builder/reducers.py b/scrapy/newitem/builder/reducers.py
new file mode 100644
index 000000000..de4670030
--- /dev/null
+++ b/scrapy/newitem/builder/reducers.py
@@ -0,0 +1,13 @@
+def take_first(values):
+    for value in values:
+        if value is not u'':
+            return value
+
+
+def return_values(values):
+    return values
+
+
+def join_strings(values):
+    return u' '.join(values)
+
diff --git a/scrapy/tests/test_itembuilder.py b/scrapy/tests/test_itembuilder.py
new file mode 100644
index 000000000..8a041c7bc
--- /dev/null
+++ b/scrapy/tests/test_itembuilder.py
@@ -0,0 +1,174 @@
+import unittest
+import string
+from scrapy.newitem.builder import ItemBuilder, BuilderField
+from scrapy.newitem.builder import reducers
+from scrapy.newitem import Item, fields
+
+
+class BaseItem(Item):
+    name = fields.TextField()
+
+
+class TestItem(BaseItem):
+    url = fields.TextField()
+    summary = fields.TextField()
+
+
+class BaseItemBuilder(ItemBuilder):
+    item_class = TestItem
+
+
+class TestItemBuilder(BaseItemBuilder):
+    name = BuilderField(lambda v: v.title())
+
+
+class DefaultedItemBuilder(BaseItemBuilder):
+    default_builder = BuilderField(lambda v: v[:-1])
+    
+
+class InheritDefaultedItemBuilder(DefaultedItemBuilder):
+    pass
+
+
+class ListFieldTestItem(Item):
+    names = fields.ListField(fields.TextField())
+
+
+class ListFieldItemBuilder(ItemBuilder):
+    item_class = ListFieldTestItem
+
+    names = BuilderField(lambda v: v.title())
+
+
+class ItemBuilderTest(unittest.TestCase):
+
+    def test_basic(self):
+        ib = TestItemBuilder()
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'Marta')
+
+        item = ib.get_item()
+        self.assertEqual(item['name'], u'Marta')
+
+    def test_multiple_functions(self):
+        class TestItemBuilder(BaseItemBuilder):
+            name = BuilderField(lambda v: v.title(), lambda v: v[:-1])
+
+        ib = TestItemBuilder()
+        
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'Mart')
+
+        item = ib.get_item()
+        self.assertEqual(item['name'], u'Mart')
+
+    def test_defaulted(self):
+        dib = DefaultedItemBuilder()
+        assert dib.default_builder
+
+        dib.add_value('name', u'marta')
+        self.assertEqual(dib.get_value('name'), u'mart')
+
+    def test_inherited_default(self):
+        dib = InheritDefaultedItemBuilder()
+        assert dib.default_builder
+
+        dib.add_value('name', u'marta')
+        self.assertEqual(dib.get_value('name'), u'mart')
+
+    def test_inheritance(self):
+        class ChildItemBuilder(TestItemBuilder):
+            url = BuilderField(lambda v: v.lower())
+
+        ib = ChildItemBuilder()
+        assert 'url' in ib._builder_fields
+        assert 'name' in ib._builder_fields
+
+        ib.add_value('url', u'HTTP://scrapy.ORG')
+        self.assertEqual(ib.get_value('url'), u'http://scrapy.org')
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'Marta')
+
+        class ChildChildItemBuilder(ChildItemBuilder):
+            url = BuilderField(lambda v: v.upper())
+            summary = BuilderField(lambda v: v)
+
+        ib = ChildChildItemBuilder()
+        assert 'url' in ib._builder_fields
+        assert 'name' in ib._builder_fields
+        assert 'summary' in ib._builder_fields
+
+        ib.add_value('url', u'http://scrapy.org')
+        self.assertEqual(ib.get_value('url'), u'HTTP://SCRAPY.ORG')
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'Marta')
+
+    def test_multiplevaluedadaptor(self):
+        ib = ListFieldItemBuilder()
+
+        ib.add_value('names',  [u'name1', u'name2'])
+        self.assertEqual(ib.get_value('names'), [u'Name1', u'Name2'])
+
+    def test_identity(self):
+        class IdentityDefaultedItemBuilder(DefaultedItemBuilder):
+            name = BuilderField()
+
+        ib = IdentityDefaultedItemBuilder()
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'marta')
+
+    def test_staticmethods(self):
+        class ChildItemBuilder(TestItemBuilder):
+            name = BuilderField(TestItemBuilder.name.expander, string.swapcase)
+
+        ib = ChildItemBuilder()
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'mARTA')
+
+
+    def test_staticdefaults(self):
+        class ChildDefaultedItemBuilder(DefaultedItemBuilder):
+            name = BuilderField(DefaultedItemBuilder.name.expander, string.swapcase)
+
+        ib = ChildDefaultedItemBuilder()
+
+        ib.add_value('name', u'marta')
+        self.assertEqual(ib.get_value('name'), u'MART')
+
+    def test_reducer(self):
+        ib = TestItemBuilder()
+
+        ib.add_value('name', [u'mar', u'ta'])
+        self.assertEqual(ib.get_value('name'), u'Mar Ta')
+
+        class TakeFirstItemBuilder(TestItemBuilder):
+            name = BuilderField(TestItemBuilder.name.expander,
+                                reducer=reducers.take_first)
+
+        ib = TakeFirstItemBuilder()
+
+        ib.add_value('name', [u'mar', u'ta'])
+        self.assertEqual(ib.get_value('name'), u'Mar')
+
+    def test_expander_args(self):
+        def expander_with_args(value, expander_args=None):
+            if 'val' in expander_args:
+                return expander_args['val']
+            return value
+
+        class ChildItemBuilder(TestItemBuilder):
+            url = BuilderField(expander_with_args)
+
+        ib = ChildItemBuilder(val=u'val')
+        ib.add_value('url', u'text')
+        self.assertEqual(ib.get_value('url'), 'val')
+
+        ib = ChildItemBuilder()
+        ib.add_value('url', u'text', val=u'val')
+        self.assertEqual(ib.get_value('url'), 'val')
+